Noble metal-containing zeolite catalysts have been in use in the petroleum industry for many years. Particular uses include alkane dehydrocyclization (see, e.g., U.S. Pat. No. 4,458,025 to Lee et al.) and hydrocracking.
Esso (now Exxon), Union Oil Company of California, and Union Carbide Corporation have all been active in the development of noble metal/zeolite catalysts, and some of their developments are given in U.S. Pat. Nos. 3,213,013 to Arey, Jr.; 3,326,818 to Gladrow et al.; 3,547,807 and 3,547,808 to Hansford; 3,929,672 to Ward; 3,963,644 to Hansford; 4,419,271 to Ward; and 4,401,556 to Bezman et al. Y-type zeolites, synthetic faujasites are particularly known as hydrocracking catalyst bases. Zeolite Y itself is disclosed in U.S. Pat. No. 3,130,007 to Breck, and modified, ultra-stable Y-type zeolites are disclosed in, inter alia, U.S. Pat. Nos. 3,293,192 to Maher et al.; 3,449,070 to McDaniel et al.; British Patent No. 2,014,970; and U.S. patent application Ser. No. 846,312, filed Oct. 28, 1977. These modified Y-type zeolites are known to be particularly satisfactory for midbarrel hydrocracking.
Although some of the early zeolite hydrocracking catalysts employed solely a zeolite as the catalyst base, it is now common to use as a catalyst base (that part of the catalyst other than the noble metal) a zeolite and an inorganic oxide binder. The more common binders are alumina, silica, magnesia, zirconia, beryllia, titania, and mixtures thereof.
The preparation of these catalysts has been described in several of the previously-mentioned patents, albeit usually in such terms as "any one of numerous procedures".
French Published Application No. 2 500 326 summarizes the art of manufacture of these catalysts, and discloses a technique wherein the catalyst base is formed and the noble metal then introduced by competitive ion exchange with a noble metal complex cation and a competitor cation chosen from at least one of ammonium, alkaline earth and rare earth ions. The catalyst is then washed, dried (and, optionally, calcined), cooled, and rehydrated before reduction and use.
U.S. Pat. No. 4,252,688 to Gallei et al. describes an alternative manufacturing technique in which the catalyst base is prepared and calcined, then impregnated with a noble metal salt solution of volume identical to the water absorption capacity of the base (pore-filled), dried, and re-calcined. The catalyst may then be reduced and used.
The disclosures of the above-mentioned patents and patent application are incorporated herein by reference.
It would be desirable to develop a process for the manufacture of a noble metal/zeolite/oxide matrix catalyst which requires the minimum number and complexity of manufacturing steps, while still affording a catalyst having a satisfactory metal distribution and minimizing loss of the noble metal.